The transdermal route of parenteral drug delivery provides many advantages over other administration routes. Transdermal systems for delivering a wide variety of drugs or other beneficial agents are described in U.S. Pat. Nos. 3,598,122; 3,598,123; 3,731,683; 3,797,494; 4,031,894; 4,144,317; 4,201,211; 4,286,592; 4,314,557; 4,379,454; 4,435,180; 4,559,222; 4,568,343; 4,573,995; 4,588,580; 4,645,502; 4,698,062; 4,704,282; 4,725,272; 4,781,924; 4,788,062; 4,816,258; 4,849,226; 4,904,475; 4,908,027; 4,917,895; 4,938,759; 4,943,435; 5,004,610; 5,071,656; 5,122,382; 5,141,750; 5,284,660; 5,314,694; 5,342,623; 5,411,740; and 5,635,203, which are hereby incorporated in their entirety by reference.
The administration of nicotine buccally, nasally and transdermally to assist a patient desiring to quit smoking has been shown to be clinically effective in reducing the rate of recidivism. Nicotine chewing gum and transdermal nicotine are two of the most widely used forms of nicotine replacement therapy currently available. Transdermal devices for administering nicotine are disclosed in U.S. Pat. Nos. 4,597,961; 4,758,434; 4,764,382; 4,839,174; 4,908,213; 4,915,950; 4,943,435; 4,946,853; 5,004,610; 5,016,652; 5,077,104; 5,230,896; 5,411,739; 5,462,745; 5,508,038; 5,599,554; 5,603,947 and 5,726,190, for example, which are hereby incorporated in their entirety by reference.
Most of the transdermal drug delivery devices of the prior art utilize an impermeable backing on the skin distal surface of the device to protect the device from damage and to prevent loss of the active ingredient(s). In order to improve user satisfaction, these backing layers are often tinted to a color similar to skin tones. However, as can be readily appreciated, it is not commercially practical to provide pigmented backing layers for transdermal systems which approximate all skin colors.
Another approach that has been taken is to provide transparent transdermal systems in which all elements forming a device are sufficiently transparent to permit the natural skin color to be visible through the device. Marketed products which take this approach include the ALORA® and CLIMARA® estrogen replacement patches and the DURAGESIC® transdermal fentanyl delivery system. When these devices are applied to the skin, the patient's natural skin color is visible through the patch, making the presence of the patch extremely inconspicuous. Government regulations require that these products bear identifying indicia, but the indicia can be printed on these devices in light colored or white ink which is not noticeable from a distance of several feet, but is still readable on close inspection.
Such transparent patches have been found useful with non-volatile drugs such as fentanyl and hormone replacement steroids, but no such transparent product has been developed for the delivery of nicotine.
Nicotine is a liquid alkaloid that is colorless, volatile, strongly alkaline, readily oxidized, subject to degradation on exposure to light and highly permeable through not only the human skin, but also many of the polymers conventionally used in the fabrication of backing layers and packaging materials for transdermal products (see for example U.S. Pat. No. 5,077,104). As a result, the backing layers of the transdermal nicotine delivery devices currently available utilize opaque, skin-colored multilaminate films which typically contain a metalized layer, such as aluminum.
Not only do the commercially available transdermal nicotine patches use opaque backings, but many of these devices, due to the complexities of handling and processing nicotine, have other components which are not transparent. For example, the original Prostep® transdermal nicotine product used a drug reservoir in the form of an opaque white gel, held in place by an opaque adhesive overlay. The HABITROL® and NICOTROL® nicotine patches incorporated absorbent pads in the drug reservoir in which the nicotine was absorbed.
It has also been proposed to co-administer nicotine with other substances that improve nicotine cessation therapy. See, for example, U.S. Pat. Nos. 4,908,213; 5,599,554; and 5,726,190 noted above; and WO 97/33581.